Adhesives



Reissued July 6, 1937 1 1 UNITED STATES PATENT OFFICE ADHESIVES Gardner R. Alden, Framingham, Mesa, assignor to Dennison Manufacturing Company, Framingham, Mass a corporation of Massachusetts No Drawing. Original No. 1,969,636, dated August 7, 1934, Serial No. 561,703, September 8, 1931. Application 'for reissue January 9, 1936,

Serial No. 58,420

21 Claims. (Cl. 218-62) This invention relates to adhesives and to a method of joining together two or more surfaces certain of them are more or less subject to weath-" er conditions, becoming sticky in dampweather,

15 which causes premature adhesion, and drying to brittleness when kept in dry places.

A typical and unusually exacting application of adhesives is found in the sealingof packages wrapped with smooth sheet-cellulose materials 20 and especially with transparent sheets of this Charch et al. or du Pont waterproof" or mois-- tureproof cellophane" No. 300). Such surfaces are so smooth and so resistant to water that they are not wetted by the usual water soluble adhe- 30 sives', which accordingly fail to have any appreciable adhesivejeifect. .An object of this invention, therefore, is to provide a class of adhesive compositions and coatings which preferably are not rendered adhesive or 36 tacky by the atmosphere and a. method for the application of the same, especially to smooth surfaces (such as waterproof cellophane) which are not wetted freely by the adhesives now available. Further objects of the invention will appear 40 from the following disclosure.

.A part of the invention includes the preparation of a potentially adhesive solution or suspension of shellac and/or other resinous materials or gums,

preferably contained in a volatile organic solvent,

.45 forming a solution of suitable viscosity and having the property of drying to form a firm, non-sticky, but preferably flexible surface.

I Another part of the invention provides a. liquid solvent or vehicle suitable for moistening the The application of the invention accordingly in 60 cludes the preliminary step of preparing an adhesive composition, typically a solution or sus-- pension of hard and/or soft gums and a specific adhesive, such as shellac, in a suitable solvent vehicle comprising one or more volatile organic solvents. The composition may then be applied in the usual way to one or both of the surfaces to be Joined. The surfaces may be brought together at this stage. For most purposes, however, such as labels, it is desirable to dry the gummed surface and leave it in this condition until it is to be used. In this case, the coating is allowed to dry (which is effected quickly) and the gummed surface .will keep indefinitely without sticking or deterioration, unlessexposed to high temperature. When required for use, it may be moistened with a suitable solvent vehicle, typically of high boiling point and adapted to serve as a plasticizer. The moistening agent may be controlled, in its softening and penetrating effects, by the addition of an inert non-solvent liquid which is preferably freely miscible therewith, such as water. A non-solvent liquid may also be employed to serve as a plasticizer. The thus prepared surface and the surface to be joined are then contacted and pressed together, and the adhesive connective layer permitted to dry and set.

A preferred instance of the practical application of the invention will be described with respect to the adhesive Joining of surfaces of cellophane which have been rendered water-proof either to unlike surfaces or to other surfaces of the same material.

For this purpose, it is found that a solution of shellac manifests specific properties of adhesion to cellulosic materials, and is especially recommended as one ingredient of the composition to which may be added a soft gum to impart plasticity (such as gum elemi) and a viscosity increasing agent (such as gum copal) to improve the strength and spreading characteristics of the composition. These are compounded as by dissolving in a suitable amount of a' freely volatile organic liquid (such as tol uol and alcohol) to a freely spreading liquid consistency.

Thus, the various materials may be first sepa-- rately dissolved as follows:

No. i No. 2 No. 3

22 lbs. copal- 25 lbs. elemi 20.5 lbs. shellac 15 lbs. toiuol 6 lbs. toluol. 35.0 lbs. alcohol 4 lbs. alcohol 1% lbs. alcohoL...

dried. The summed sheet thus obtained has a the gummed sheets may be piled one upon another without adhesion or solidifying of the mass and labels or the like may be cut out, embossed,

, printed, etc., without difliculties of this sort.

The shellac, when applied alone, may be satis- ,factorily employed with the moistening solution described below, but the addition of the soft gum elemi (which may be in part or wholly replaced by a similar permanently soft gum such as soft gum copal) imparts plasticity to the dried deposit, while the gum copal (especially if a hard copal is used) increases viscosity of the solution and tenuity of the applied liquid film, during spreadmg.

The solventsnamed are preferable, in that they avoid the disadvantages of certain other organic solvents, such as the toxicity of benzol, and at the same time are freely fluid and rapidly volatile. These are especially advantageous features when a dried gummed surface is required as in making gummed labels and the like. But other solvents exhibiting these properties may be selected from the wide range of organic solvents now available and applicable to this purpose When ready for use, as for example in the application of the labels to cellophane wrappings, the gummed surface is wet with the moistening solution, the solvent or penetrating effect ofwhich may be modified by the addition of water.

An especially satisfactory solution for this purpose may be prepared as follows:

IV. Moistening solution Per cent Butyl cellosolve (butyl ether of ethylene glycol B. P. l65173 C.) Water 50 Small quantities of other high boilers or plasticizers can likewise be used. I

This softens the gumming layer but does not dissolve it sufficiently to form a solution which 7 vehicle remains, in liquid condition, and thus preserves a certain degree of softness and flexibility in the connective adhesive layer which prevents subsequent embrittling of the label, and hence promotes permanent and firm adhesion between the two surfaces.

While the adhesive composition will, in perhaps its most common application, be applied to sheet materials such as labels of paper or cloth, it may likewise be applied to surfaces which are not usually wetted by water such as waterproof cellophane above mentioned or other cellulosic com positions, or even to metal surfaces such as aluminum foil, or to surfaces generally which are not wetted by water but which are wetted by the solvent and plasticizer liquids employed, such as cellulose esters and others.

The resinous materials, also while preferably containing shellac, may also include manila copal, dammar gum and synthetic resins, and ill be ed severally but preferably in admiuti '2 or The plasticizers may be either high boiling point solvents of the resinous material or materials employed, or non-volatile miscible liquids, and include the glycerol ,esters of fatty acids, castor oil, and linseed oil. Appropriate solvents may be used which serve additionally to wet and to soften the surface to which the adhesive is to be applied.

For example, in given cases, other gumming compositions within the purview of the invention may be made up as follows:

Gun-i copal or 28 parts gum copal Shellac 22 parts shellac Gum elemi 10 parts castor oil (Castor oil) 6 parts toluol 33 parts'denatured alcohol and applied in the usual way,,the resulting coating being wetted with moistening solutions such as:

Alcohol Alcohol Toluol Toluol Tricresyl phosphate Butylphthalate used for moistening-the adhesive compositions, as follows:-

Butylether of ethylene glycol 40 Alcohol 20 Water ..L 40 Alcohol 40 Butanol 10 Toluol 30 Castor oil 20 Butylphthalate l Monoethyl ether of ethylene glycol Monobutyl ether ofethylene glycol Monoethyl ether of diethylene glycol Monobutyl ether of diethylene glycol Monoethyl ether of diethylene glycol Monoethyl ether of ethylene glycol Monobutyl ether of ethylene glycol Water Diethylene glycol Triethanolamine It is to be understood that the adhesive composition, in each case, may be applied to either or both of the surfaces to be joined and may be immediately applied (if desired) or dried and subsequently wetted with the moistening solution and then applied, or the moistening solution alone may be applied to one surface and the adhesive composition applied to the other and dried before contact.

Parts Itmay be further observed that, either simultaneously with the initial application of the adhesive composition or subsequently theretoe-(and either with or without complete drying of the same) -the composition may be rendered plastic by the application of heat and pressed or molded to such conformation as may be desired. Such heating may be partly or wholly relied upon to develop the adhesiveness of the composition, thus dispensing with the necessity of adding the moistening solution,or may be so regulated as to aflect the plasticity only.

For example, a sheet of cellophane or other sheet material towhich the adhesive. composition has been applied may be molded by light compression, or embossed, or otherwise shaped and molded, in usual ways. For'example, embossed adhesive labels may be so made. On the other hand, the coated sheet may be allowed to dry (with or withouteffecting adhesion to anotherv surface) and the whole heated later on to a. sufficient degree to soften the composition, whereupon the sheet or sheets may be shaped as desired and subsequently hardened by cooling. Again the coated and dried sheet may be heated sufiiciently to render the'coating adhesive and then applied to another surface to which it readily adheres, or simultaneously heated and applied, and remains securely attached, upon cooling and hardening. j v It should be understood that the present disclosure is, for the purpose oi'illustration only and that this invention includes all modification and equivalents which fall within the scope of the appended claims.

I claim:

1. Method. of joining two surfaces together, comprising the steps of applying to one of said surfaces an adhesive composition containing shellac in a volatile liquid vehicle, drying, and moistening with a'moistening solution contain-" .ing a solvent for the dried adhesive and a piasticizer.

2. A method of joining two surfaces together by adhesion, comprising the steps of applying to one of said surfaces an adhesive composition containing shellac and a gum, both in a volatile liquid vehicle, drying, and moistening with a moistening solution containing a solvent for said w one of said surfaces an adhesive composition containing shellac and a gum, both in a volatile liquid vehicle and a liquid of high boiling point as a plasticizer. J.

4. A'method of joining two surfaces together by adhesion, comprising the stepof applying to one of said surfaces an adhesive composition containing shellac, a hard gum and a soft gum, all in a volatile liquid vehicle, and a liquid of high boilingpoint as a plasticizer.

5. A method of Joining two surfaces together by adhesion, comprising the steps of applying a coating of shellac and a gum to one of said surfaces, and. then moistening with a liquid containing a softening agent with respect to the other surface, and contacting the second surface therewith.

6. A method of joining two surfaces together by adhesion, comprising the step of applying to one of said surfaces an adhesive composition containing shellac and gum elemi in a volatile liquid vehicle.

' cellophane.

7. A method ofjolning two surfaces together by adhesion, comprising the step of applying to one of said surfaces an adhesive composition containing shellac, and gum elemi and gum copal in a volatile liquid vehicle.

8. A method of joining two surfaces together by adhesion, comprising the steps of applying to one of said surfaces an adhesive composition containing shellac and a volatile liquid vehicle, drying, and subsequently applying thereto a moistening liquid containing butyl ether of ethylene glycol.

9.. A method of joining two surfaces together by adhesion, comprising the steps of applying to one of said surfaces an adhesive composition containing shellac, and a volatile liquid vehicle, drying, and subsequently applying thereto a moistening liquid containing butyl ether of ethylene glycol, and water.

10. A method of joining two surfaces together by adhesion, comprising the steps of applying to 11. A method of joining two surfaces'together ,by adhesion, comprising the steps of applying to one of said surfaces an adhesive composition containing shellac, and a volatile liquid vehicle, drying, and subsequently applying thereto a moistening liquidcontaining ethyl ether of ethylene glycol, andwater.

12. A method of labeling which comprises placing a moist water insoluble resinous material upon the back of a label, drying said mate rial, moistening the said dried material with a plasticizer solution and then applying the label.

13. A method of adhesively attaching a paper label to a sheet of cellophane which comprises coating the back of the label with a solution of a resinous material in a volatile solvent, permitting the solvent' to evaporate, moistening the residual resinous layer with a solution of a plasticizer in a volatile solvent, and applying the moistened label to a sheet of cellophane.

14. A method of labeling which comprises placing a moist water insoluble resinous material, containing shellac upon the back of a label, drying said material, moistening the said dried material with a plasticizer solution and then applying the label. 7

15. A method of adhesively attaching a paper label to a sheet of waterproof cellophane" which comprises coating the back'of the label with a solution of a resinous material in a volatile solvent, permitting the solvent to evaporate, moistening the residual resinous layer with a solution of a plasticizer in a volatile solvent and applying the moistened label to asheet of waterproof 16'.A method of adhesively attaching a paper label to a sheet of waterproof cellophane" which comprises coating the back of the label with a solution of a resinous material containing shellac in a volatile solvent, permitting the solvent to evaporate, moistening the residual resinous layer with a solution of a plasticizer in a volatile solvent and applying the moistened label to a sheet of waterproof cellophane. 4

1'7. A method of labeling which comprises placing a solution of water' insoluble, resinous material upon the back of d. label, drying said one of said surfaces an adhesive composition material, providing in said-dried material a mois- 7 tened layer of resinous material including a volatile solvent for said dried material and a plasticizer and then applying the label.

18. A method of labeling which comprises plac- 5 ing a moist coating of water insoluble resinous material upon the back of a label, drying said coating, moistening the said dried coating with a plasticizer solution andthen applying the label.

' 19. A method of labeling which compriseiLplac- 7 lo ing a solution 01' a water insoluble resinous material upon the back of. a label, drying said material, providing insa'id dried material a moistened layer or resinous material including a 'volatile solvent for said dried material and a 15 plasticizer and then applying thelabel.

20. A method of labeling which comprises forming upon the back of a label a dry coating of water insoluble resinous material, moistening' material and a plasticizer, and then applying the I label.

GARDNER R. ALDEN. 

